Ski jumping hills should be prepared for competitions in accordance with project documentation in order to ensure safe and fair conditions for competitors. Geodesy/surveying is essential for guiding ...preparations and controlling the actual shape of the hill. In this article, we present a methodology for the control measurements and preparation of an inrun for a ski-flying hill in Planica. On each side of the track, there is metal tube that guides the trolley, which mills tracks into the ice. A special platform containing three measuring prisms was designed to control the position of the tubes. The proposed method was thoroughly analyzed in terms of its measurement quality and compared to previously used methodologies. The empirical results suggest that our proposed platform provides inrun geometry with a higher quality than previously used methods.
The main goal of our research was to design and implement an innovative target that would be suitable for accurately registering point clouds produced from unmanned aerial vehicle (UAV) images and ...terrestrial laser scans. Our new target is composed of three perpendicular planes that combine the properties of plane and volume targets. The new target enables the precise determination of reference target points in aerial and terrestrial point clouds. Different types of commonly used plane and volume targets as well as the new target were placed in an established test area in order to evaluate their performance. The targets were scanned from multiple scanner stations and surveyed with an unmanned aerial vehicle DJI Phantom 4 PRO at three different altitudes (20, 40, and 75 m). The reference data were measured with a Leica Nova MS50 MultiStation. Several registrations were performed, each time with a different target. The quality of these registrations was assessed on the check points. The results showed that the new target yielded the best results in all cases, which confirmed our initial expectations. The proposed new target is innovative and not difficult to create and use.
A prototype of a low-cost GNSS (Global Navigation Satellite System) monitoring system was installed on a deep-seated landslide in north-western Slovenia to test its performance under field ...conditions. The system consists of newly developed GNSS stations based on low-cost, dual-frequency receivers and open-source GNSS processing software. It automatically receives GNSS data and transmits them over the Internet. The system processes the data server-side and makes them available to the end user via a web portal. The detected surface displacements were evaluated through a comparison with the network of classic geodetic measurements. The results of a nine-month monitoring period using seven GNSS stations provided a detailed insight into the spatial and temporal pattern of deep-seated landslide surface movements. The displacement data were correlated with precipitation measurements at the site to reveal how different parts of the landslide react to rainfall. These data form the basis for the further development of an early-warning system which will help to manage the risk the landslide poses to the local population and infrastructure.
Traditional measurement methods are still widely used for recording cultural heritage objects. On the other hand, geodetic surveying and modern technologies such as 3D laser scanning can provide more ...accurate, geometrically consistent and extremely detailed data that can be used as a basis for detailed vector maps or 3D models. The main aim of our research was to investigate the complementary approach, using both traditional and modern methods, in order to produce detailed vector maps of the Romanesque church of St. Martin in Chapaize, France, which are essential for further unveiling its historic development. Geometrically, this church is rather extensive and has many irregularities in its shape. Our approach to the documentation process is presented and evaluated in this paper. We applied the Procrustes analysis for the ground floor map, which gave us an objective accuracy assessment. Point clouds of the bell tower acquired by two different laser instruments have also been compared.
In Ribčev Laz near Lake Bohinj there is a model of Triglav, the highest mountain in Slovenia. Made of stones, it is the work of the painter Valentin Hodnik from Bohinj. Although it is a work of art, ...we wanted to evaluate the correctness of its shape compared to the actual mountain. We photographed it and created a point cloud model using the Structure from Motion process (SfM). By transforming the point cloud to actual size, we were able to compare it with the actual shape of the Triglav mountain range obtained from Laser Scanning of Slovenia (LSS). As expected, the shape of the model varied considerably from the actual shape of the mountain, and the scale of the individual slopes and ridges was not the same. For a qualitative evaluation of the model, we calculated the distances between the transformed model and actual surface. The average absolute distance between the nearest points in both point clouds was 41.8 m (6 cm at a built-model scale) with a standard deviation of 38.0 m (5.4 cm). The results are represented by a picture of absolute distances. We also produced a smaller 3D print of the Triglav model and the actual shape of the mountain.
U Ribčevom Lazu kraj Bohinjskog jezera nalazi se maketa Triglava, najviše planine Slovenije, izgrađena od kamena, rad slikara Valentina Hodnika iz Bohinja. Iako je umjetničko djelo, odlučili smo procijeniti točnost njezinog oblika. U tu smo svrhu snimili maketu fotografskim aparatom i korištenjem procesa struktura iz kretanja (SfM) stvorili oblak točaka. Pretvarajući taj oblak točaka u stvarnu veličinu planine, uspoređivali smo oblik makete sa stvarnim oblikom planinarskog područja Triglava dobivenim iz podataka laserskog skeniranja Slovenije (LSS). Kao što se očekivalo, oblik makete značajno odstupa od stvarnog oblika planine, a ni mjerilo pojedinih padina i grebena nije isto. Za kvalitativnu procjenu makete izračunali smo udaljenosti između najbližih točaka transformiranog modela makete i stvarne površine. Prosječna udaljenost između najbližih točaka oba modela je 41,8 m (6 cm u mjerilu makete) sa standardnom devijacijom od 38,0 m (5,4 cm). Rezultati su prikazani s pomoću slike apsolutnih udaljenosti. Osim toga, izradili smo i umanjen 3D otisak makete Triglava i stvarnog oblika planine.
During new Austrian tunnelling method excavation, it is necessary to carry out an analysis of the compliance of the actual surfaces with the theoretical lines prescribed in the support types for each ...tunnel excavation step. With our own software solutions, we created point clouds of the excavation and shotcrete of the primary tunnel support through the automated process of photogrammetric data. Together with the tunnel axis and theoretical profiles, the georeferenced and filtered point clouds were then used in the analysis of the deviation from the theoretical lines of excavation and primary support shotcrete and shotcrete thickness. The final products of the independent analysis are deviation profiles and unwrapped extrados views with numerical results and a color legend.
The RANSAC (RANdom SAmple Consensus) is often used to identify points belonging to the objects whose shape can be modeled with geometric primitives. These points, called inliers, are of great ...interest in some applications but often the goal is also to estimate the parameters of geometric shape and their accuracies. The quality of RANSAC results is rarely analysed. The accuracies of estimated parameters are usually calculated based only on the residuals of inliers, selected by RANSAC, from a mathematical model. However, the analysis does not indicate if the right points were selected. The result of RANSAC depends on the random selection of the minimum number of points that uniquely describe a mathematical model; in the case of multiple repetitions of the method, the results are not necessarily the same. This paper presents an analysis of RANSAC reliability based on repeating the selection of points from the point cloud by RANSAC one hundred times. A standard deviation of one hundred parameter values is used to estimate the parameters’ accuracies. An analysis is made for three different examples of geometric objects: a sphere, a cone, and a plane. Finally, we suggest repeating the algorithm several times and checking the consistency of the results to obtain a more reliable estimation of parameters and their accuracies.
This article describes the geodetic network of the Urbas landslide. It is the largest landslide in the Koroška Bela region, which, if triggered, can endanger human lives and damage infrastructure. ...In order to monitor the landslide, a geodetic network was established in the area of the Urbas landslide, on the basis of which the movements of control points can be calculated. After various analyses, only two small areas near the Urbas landslide proved to be stable, so we established four reference points there. In this research we defined the geodetic datum of the geodetic network of the Urbas landslide. The geodetic datum was defined on the basis of four measurement epochs processed with our own software.
Extreme events such as flash floods and debris flows are frequent phenomena that occur in steep torrential catchments; these kinds of events can cause notable geomorphic changes. Repeated terrestrial ...laser scanning (TLS) surveys were performed in a steep forested catchment of the Kuzlovec torrent (drainage area ~0.7km2) in central Slovenia, where a ~200-m long section of the torrent was scanned in 2013, 2014, and 2015. The main aim of this study was to perform the geomorphic response detection in the torrent due to hydro-meteorological events of different magnitudes. After applying several pre-processing steps, digital terrain models (DTMs) with a cell resolution of 5cm were produced. The geomorphic change detection was performed using the DTM of Difference approach (DoD). Several above-average flow events occurred in the period from 2013 to 2015 (some of them can be regarded as floods). The 2014 August extreme flash flood that was initiated by the rainfall event with a return period exceeding 100years, where maximum 1-minute rainfall intensities were up to 288mm/h, led to erosion rates of an order of magnitude higher than average annual erosion rates. Moreover, the analysis of the geomorphic changes shows that the August 2014 flash flood caused intense sediment transport processes that resulted in the changes at the location of the main stream channel thalweg and reduced channel roughness. The unit stream power for the scanned section of the torrent was assessed to be approximately 500W/m2 during this extreme event. This is above the thresholds that were suggested to differentiate between the situations where significant geomorphic changes can occur and the situations where geomorphic changes are not notable.
•Repeated TLS surveys were performed to detect geomorphic changes.•The flash flood changed the geomorphic characteristics of the torrent channel.•Erosion rates due to the flash flood event were much higher than average annual rates.•High spatial resolution data are a useful tool to detect changes in steep forested torrents.
Creating digital models of important cultural heritage objects for documentation or reconstruction purposes is usually challenging: the object can be a complex building, may be placed on remote ...areas, entirely or partly difficult to access, survey has to be done in different conditions, etc.; however, final resulting models should provide adequate geometrical accuracy and completeness. Using a combination of different technologies and methods, where accuracy estimation of each methodology and often also an establishment of basic geodetic network are fundamental for ensuring the geometrically accurate final product (model), we can create three-dimensional (3D) models for documentation, inspection, maintenance and restoration purposes. Attractive 3D augmented reality (AR) and other presentations can be created, too. These outputs can be used by authorities, maintainers, conservators, investors and also public communities. Procedures and results are presented in selected cultural heritage objects in Slovenia: Chapel on Krvavec, Smlednik castle, Brestanica castle and Ljubljana castle.
PDF
